1. Field of the Invention
The present invention relates to a porous membrane adapted for use in a chemical reaction process.
2. Description of the Prior Art
In the field of gas-separation in which a gas diffusion method is adapted to separate a specific gas from a mixture of gases, there has been utilized a porous membrane which is formed with interconnected micropores having an average pore size of between several ten .ANG. and several hundred .ANG., smaller than the mean free path of gas molecules. In Japanese Patent Early Publication No. 59-59223, disclosed is such a porous membrane adapted to separate hydrogen gas from a mixture of hydrogen and nitrogen or carbon monoxide the molecular weight ratio of which is relatively large. The separation of hydrogen gas from the mixture is carried out based on the difference in rates of permeability of the gases in Knudsen flow.
In recent years, it has been found that the characteristic of the porous membrane in gas separation is useful for a chemical reaction process. Where the reaction rate of a catalytic reaction process (A.revreaction. B+P) is noticeably decreased due to the pressure of product gas P or the reaction is restricted by equilibrium, the porous membrane is effective to exhaust the product gas P from the reaction system therethrough to enhance the percent conversion of the product gas and the efficiency of separation and concentration of the product gas P. On Pages 58-61 of Chemical Engineering issued on February, 1984, such as reaction process is disclosed as a decomposition reaction process of hydrosulfide (H.sub.2 S=H.sub.2 +S), wherein, as shown in FIG. 7, the porous membrane is in the form of a porous glass pipe 1 which is filled with catalytic particles 2 of molybdenum sulfide to effect the decomposition reaction of raw material gases supplied therein and to concentrate the product gas dependent upon the difference in pressure between the interior and exterior of pipe 1.
In the reaction process described above, however, insufficient separation of the product sometimes occurs due to insufficient membrane area per unit volume of porous membrane and insufficient contact of the product gas with the porous membrane. This results in low percent conversion of the product gas. Additionally, the presence of catalytic particles 2 results in loss of pressure of the raw material gases passing through the glass pipe 1, and the pores of glass pipe 1 are clogged with powder of the catalytic particles.